As the incidence of HIV increases, one of the major steps in preventing a widespread epidemic is to make certain that medical students are prepared to recognize and treat HIV infections and their related conditions, and to counsel patients about avoiding risks that might lead to infections. This cross-sectional study assessed the knowledge level of 357 medical students and their attitudes about AIDS and HIV enrolled in a Medical College in Karachi, Pakistan. Only 6% of the students had complete knowledge on symptoms of HIV/AIDS and 7% of the students had complete knowledge on the modes of transmission of HIV. Statistical analysis of demographic factors affecting knowledge was done. Linear regression and Maentel - Haenszel tests showed that older and clinical students were more knowledgeable of symptoms and modes of transmission of HIV/AIDS. Ten attitudes were correlated with knowledge and none of these showed an association. These results on knowledge indicate that education about HIV/AIDS should be incorporated in the curriculum and interventions must be taken by public health professionals to avoid poor treatment outcomes.